Extrusion press

ABSTRACT

An upright extrusion press for extruding an extrudable mass such as a plasticized and/or pulverized mass includes a pressing table mounting an extrusion die and at least two pressure or extrusion pots jointly swingable about a common vertical axis for alternately moving the pots into a filling position and an extrusion position, respectively. Each of the pots comprises an extrusion bottom including an opening which is so disposed that it is in registry with the extrusion opening in the die when the pot is in its extrusion position.

United States Patent 1 [45] Jan. 2, 1973 f 22 Filed:

[21] App1.No.: 61,711

541 EXTRUSION PRESS [75] Inventor: Eugen Kopp, Stuttgart, Germany [73]Assignee: Werner 8: Pfleiderer, Stuttgart- Feuerbach, Germany Aug. 6, 1970 [30] Foreign Application Priority Data Aug. 16, 1969 Germany ..P 1941 872.5

[52] US. Cl. ..425/376, 264/245, 425/132 [51] Int. Cl. ..B29f 3/014 [58]Field of Search.l8/12 DR, 12 P, 30 G0, 30 GR, 18/30 FJ; 25/15, 17 C;425/152, 344, 376, 382, 261, 166, 256; 264/323, 245

[56] References Cited UNITED STATES PATENTS 2,477,258 7/1949 MacMillin"18 /311 FJ Primary Examiner-J. Spencer Overholser Assistant Examiner-B.D. Tobor Attorney-Hane, Baxley & Spiecens [57] i ABSTRACT An uprightextrusion press for extruding an extrudable mass such as a plasticizedand/or pulverized mass includes a pressing table mounting an extrusiondie and at least two pressure or extrusion pots jointly swinga-v bleabout a common vertical axis for alternately moving the pots into afilling position and an extrusion position, respectively. Each of thepots comprises an extrusion bottom including an opening which is sodisposed that it is in registry with the extrusion opening in the diewhen the pot is in its extrusion position.

17 Claims, 5 Drawing Figures EXTRUSION PRESS The invention relates to anextrusion press for extruding a mass of extrudable consistency such as aplasticized and/or pulverized mass and more particularly to an uprightextrusion of this kind with an extrusion die mounted in a pressing tableand two or more pressure or extrusion pots which are swingable relativeto the die and parallel to their-axes about a common vertical pivot axisfor alternately moving the pots into an extrusion position and a fillingposition, respectively.

BACKGROUND With extrusion presses of the general kind above referred to,the mass is extruded in the form of a strand or any other profile ascontrolled by the die from a pot in the extrusion position while a potin the filling position is being charged with the mass; if desired themass in the pot in the filling position can be pre-compressed by meanssuitable and known for the purpose. After charging a pot in the fillingposition the filled pot is moved into the extrusion position while thepot which is now empty by extruding the mass therein is moved into thefilling position. As is evident, such an arrangement permits rapid andconsecutive extrusion operations. As it is also evident, the principleof swinging pots about a common axis can be extended to more than onefilling position and extrusion position.

Multiple extrusion presses of the above referred to type as now knownhave several disadvantages. The bottom opening of the pots is as largeas the cross sectional area of the space within the pot or in otherwords, the pots constitute an open ended tube. Accordingly, mass filledinto such pots is retained therein merely by adhesion of the mass to theinner wall of the pots. Reliance on such inherent adhesion of the massis, at best, acceptable only if the mass is of highly viscousconsistency. In practice it has been found that even with a mass of thiskind there is a tendency of the mass to slide, at least partly, out ofthe pots especially when and while the same are being swung from thefilling station into the extrusion station. Moreover, an often desirablepre-compression of the mass is rarely, if ever, possible to the desiredextent without dislodging of the mass. As it is evident, downwardsagging of the mass interferes with a smooth progress of the extrusionoperation; it causes loss of time and may also result in damage to thepress. I I 1 The afore pointed out disadvantage of presses as justdescribed is particularly'pronounced when the masses to be extruded haveinherently a low friction coefficient.

There are also known multiple extrusion presses in which the totalareaofthe bottom opening of the swingable pots, which as previously stated isusually equal to the entire cross sectional area of the pot, is coveredby an extrusion die mounted in the pots themselves or suspended from thebottom side of the pots. Assemblages of this kind require extremelyexpensive extrusion dies.. Moreover, they are in conflict with a generaldemand in the industry that for operational reasons the extrusion diesshould be mounted on the pressing table itself. In other words, pressesof the 'kind just described while theoretically possible arenotsatisfactory for practical purposes.

THE INVENTION It is a broad object of the present invention to provide anovel and improved upright extrusion press of the general kind abovereferred. to which permits swinging of the pressure or extrusion potsfrom a filling station to an extrusion station without danger of escapeof the mass to be extruded even though the friction coefiicient thereofmay be comparatively low.

Another important object of the invention is to provide a novel andimproved upright extrusion press of the general kind above referred towhich permits simultaneous extrusion of the mass through several dieopenings without danger of substantial pressure differentials in theopenings as the mass passes through the same. Obviously, such pressuredifferentials would result in variations in the density and otherproperties of the extruded strands or other profiles.

SUMMARY OF THE INVENTION The afore pointed out objects, features andadvantages and other objects, features and advantages which will bepointed out hereinafter are obtained by providing in the pressure orprotrusion pots apertured bottoms which automatically prevent prematureescape of the mass from the pots. The bottoms are preferably so mountedin the pots that they can be axially displaced therein within selectedlimits.

The invention also provides that the passage opening for the mass ineach bottom is centrally located and in registry with the. die when therespective pot is in the extrusion position and that the cross sectionalarea of the openings in the bottoms is larger than the cross sectionalarea of the extrusion passage in the die so that the cross section ofthe bottom opening cannot interfere with the smooth operation of the dieand thus af fect the cross sectional configuration of a strand or otherprofile emerging from the die.

According to another aspect of the invention the extrusion bottomincludes several openings. In such arrangement, the die must, of course,have several passages so that a plurality of strands or other profilescan be simultaneously extruded.

The afore pointed out vertical adjustability of the extrusion bottoms inthe pots themselves has among others, the important advantage that evenwhen the pressure or extrusion pots and the pressure bottoms thereinhave a large cross section sealing of the pots against the die duringthe extrusion, operation is obtained and that a smooth u'niformtlow ofthe mass to be extruded is assured.

According to another aspect of the invention the same advantage isobtainedby providing in the side of the bottom facing the die a recessdefining a pressure equalizing space which is disposed concentricallywith reference to the opening in the bottom and so arranged that when apot is in its extrusion position, that is, when the opening in thebottom is in registry with the die mounted on the pressing table, therecess is sealed off along its entire outer periphery.

, According to a further exemplification of the invention which isespecially advantageous for large cross sections of pressure orextrusion pots and correspondinglylarge pressure bottoms, the aforereferred disposed annular spaces of different diameters and sealed offagainst each other, each of said recesses communicating with openings inthe bottom and the die. These annular recesses are preferably sodimensioned that the diameters thereof decrease toward the center of thebottom, that is, that the recesses having the largest diameter arenearest to the outer rim of the bottom whereas the recess with thesmallest diameter is nearest to the center of the bottom. The openingsthrough the bottom and the die, which issue into the recesses as stated,have advantageously also difi'erent diameters. It has been found that byproviding such an arrangement of the openings and the recesses differentvelocities of the mass flows at the outlets of the die are effectivelyavoided even when the pressure bottoms are of large size. The inventionalso contemplates that the lower rims of the openings through thepressure bottoms and/or the edges defining the equalizing spaces aresharp edged so that they act as cutters and thus automatically cut ofithe strands or other profiles as the pots are being moved from theextrusion position toward the filling position.

According to the invention, it is also advantageous to provideadditional means for preventing escape of the mass from the pots. Thesemeans are in the form of closure plates which. abut against the openingsthrough the pressure bottoms when the pots are in the filling position.These closure plates are preferably displaceable and adjustable so thatthey can be correctly located depending upon the location of theopenings in the bottoms.

DETAILED DESCRIPTION OF THE INVENTION In the accompanying drawingseveral embodiments of the invention are shown by way of illustrationand not by way of limitation. 1

In the drawing:

FIG. 1 is an elevational diagrammatic view, partly in section, of anextrusion press according to the invention;

, FIG. 2 is a fragmentary elevational view of the press according toFIG. 1 but with a modified die;

FIG. 3 is an elevational diagrammatic view of the press accordingto FIG.1 but modified with respect to the pressure bottom and the die;

FIG. 4 is an elevational view showing a further modification'of thepressure bottom and the die of the press; and I FIG. 5' is a plan viewupon FIG. 3 seen in the direction of arrow V. I I

Referring now to the figures more in detail and first to the extrusionpress as exemplified in FIG. 1, the press according to this figurecomprises a pressing table 22 in which an extrusion die I is fixedlymounted. This die should be visualized as being conventional and mayhave any desired passage therethrough. Two pressure or extrusion pots 2of equal structure are swingable about a vertical column 3 as a commonpivot axis. The left hand pressure pot is shown in its extrusionposition and theright hand pot in its filling position, that is, in theposition in which it is being filled with the mass to be extruded. Aplunger 4 serves to pre-compress the mass-inthe pot in thefillingposition.

While only two pots are shown, it is readily apparent that the conceptof the invention also encompasses an arrangement with more than twopressure or extrusion pots and more than one filling position orstationand one extrusion position or station.

The extrusion station includes a ram 8 which can be lowered and raisedin a conventional manner by devices suitable for the purpose (notshown). Lowering of the ram into the left hand pot 2 extrudes the masstherein through an opening or nozzle 9 in a pressure bottom 2" integralwith the pressure pot and die 1. The mass emerges from the die in theform of a strand 10. The figure shows the mass partly extruded and ram 8lifted above pot 2. This position has been selected for clarity ofillustration; it reflects an interrupted extrusion operation which willrarely occur in practice.

The pressing table 22 with the components mounted thereon is suspendedby tie bars 11 or other suitable means on the head assembly (not shown)of the press. A frame structure 12 supports both pots and is journalledon column or shaft 3. I 1

Opening 9 in extrusion or pressure bottom 2 may be closed off by 8'CIOSUI'6 plate 13 when the pot is in its filling position (right handpot). Set screws 14 or other suitable adjustment means secure theclosure plate in a selected position. The pot in the filling positioncan be charged with the mass to be extruded by simply pouring the massinto the potfThe initially very loose mass may then be pre-compressed bymeans of plunger 4 as previously described, or if preferred,'the pot canbe evacuated'prior to the extrusion. 1

As it is shown in FIG. 1 the pot assembly is up and down slidable oncolumn or shaft 3 by suitable lifting means but for the extrusion andfilling operations it is lowered into the position of FIG. 1 against theaction of a spring 15 so that the pots to beextruded or filled are insealing engagement with die 1 and closure plate 13, respectively.

The coacting sealing surfaces on the bottom of the respective die andthe die may be plane as shown in FIG. 1 but a conical sealing surfacecan also be provided as it is illustrated in FIG. 2 which shows aconically shaped die 1a. I

In the event plane surfaces are used as sealing surfaces, lips 17 arepreferably provided at the lower edge of opening 9. These lips as theyare exposed to the mass pressure, improve the sealing. They preferablyend in a die 1 so that a sealing between the pot and the die isautomatically obtained. The existing sealing pressure may be expressedby the equation: I

I where F l is the annular area 16 of bottom 2', p the FIG. 3 shows apress of this kind. A pressure bottom 19 is axially displaceable withina pressure or extrusion pot 2a. The bottom has a central passage openingor nozzle 20 through which the mass is pressed into a pressureequalizing space defined by a recess 5 formed in the side of the bottomfacing a die lb. This die has four passages 21 each communicating withthe equalizing space. As it is evident, four strands will besimultaneously extruded. To obtain a ratio between surface areas F 1 andF 2 (as previously defined) which is favorable for the quality of thesealing, a sealing ring 23 in bottom 19 prevents creeping of mass fromthe space in the pot above bottom 19 into an annular space 24. A ring 26within this space and retained in the inner wall of pot 2a in an axialfixed position, as it is clearly shown in FIG. 3 and also in FIG. 4,prevents a downward sliding of bottom 19 out of pot 2a when and while apot is moving between a filling station and an extrusion station.Moreover, ring in conjunction with a shoulder 25a limits lifting of thebottom within the pot to the distance 26. Such upward displacement ofthe bottom relative to the pot occurs in the extrusion station when thepot is lowered upon the die by means of the afore mentioned liftingmeans thereby assuring that the an- 25 nular surface 27 of the die whichin FIG. 3 represents the afore defined sealing surface F 2 is engagedwith pressure engagement by the bottom thereby preventing outwardcreeping of the mass.

FIGS. 4 and 5 show an extrusion press in which the die 1c and thepressure bottom 28 both have several passage openings 29 and 30,respectively. As it is shown, the passage openings 29 have a largerdiameter than the passage opening 30 and in FIG. 5 it is further shownthat the passage openings 29 and 30 are disposed in two concentriccircles. The circle including passage openings 29 is the one disposedcloser to the peripheral outside of bottom 28. More than two suchconcentric circles and correspondingly differently dimensioned passageopenings 29 and 30 may be provided in bottom 28, and, of course, in suchcase corresponding passage openings 21 must also be provided in dielaEach of the passage openings 29 communicates with an annular recess 6which constitutes a pressure equalizing space for all passage openings29. Similarly, all passage openings 30 communicate with annular recess 7which constitutes a pressure equalizing space for all openings 30. As isevident, recess 6 is larger than recess 7. Die openings 21 communicatewith recesses 6 and 7 as shown.

Mass when passing through the narrower passage openings 30 into thesmaller space 7 will experience more friction than mass passing throughopenings into larger space 6. Accordingly, there is a higher pressuredrop for the mass entering space 7 than for the mass entering space 6and such differential pressure drop is intended and utilized.

By suitably correlating the diameters of openings 29 and 20 a uniformmass pressure in both spaces 6 and 7 can be obtained which, in turn,results in a substantial uniform velocity of the strands at thedischarge ends of die 10.

The afore described steps for obtaining a substantially uniform exitflow velocity of the strands is advantageous, especially with pressurebottoms of large diameters. With such large bottoms the flow velocity ofthe strands at or near the middle of the die has been found to be higherthan the velocity of the strands leaving the die closer to the innerwall of the pressure pot, these differences in the exit velocities ofthe strands from the middle of the die toward the rim thereof can begraphically shown as a parabolic curve. This velocity differential ispresumably due to the fact that the friction between the moving mass andthe inner wall of the supply container for the mass such as the pressureor extrusion pot in an extrusion press causes a loss of energy whichdecreases toward the middle of the mass.

While the invention has been described in detail with respect to certainnow preferred examples and embodiments of the invention, it will beunderstood by those skilled in the art, after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention, and it isintended, therefore, to cover all such changes and modifications in theappended claims.

What is claimed is:

1. An extrusion molding press comprising in combination:

a pressing table having at least one extrusion opening therethrough;

at least two substantially alike pressure pots open at one end andclosed at the other end by a bottom wall, said bottom wall having atleast one extrusion nozzle therethrough and facing the pressing tableparallel thereto;

a frame structure mounting said pressure pots in spaced apartrelationship;

a pivot means disposed intermediate said pressure pots and supportingthe frame structure and thus the pressure pots pivotal about an axisnormal to the pressing table for selectively pivoting either one of thepressure pots into a first position in which said extrusion nozzle is inregistry with the table opening or into a second position in which theextrusion nozzle is out of registry with the table opening, said firstposition constituting an extrusion position and the second position afilling position respectively for the pressure pots; and

a pressure means movable into and out of a pressure pot in the extrusionposition for compacting and extruding mass contained in said pot.

2. The extrusion press according to claim 1 wherein each of said bottomwalls is axially displaceable with the respective pressure pot.

3. The extrusion press according to claim 2 wherein limit means limitaxial displacement of the bottom walls within the pressure pots.

4. The extrusion press according to claim I wherein the nozzle in eachof said bottom walls is centrally located and has a peripheral outlinelarger than the peripheral outline of an extrusion opening in thepressing plate through which the mass is to be extruded.

5. The extrusion press according to claim 1 wherein a die is fitted inthe extrusion opening in the pressing table, said die including two ormore extrusion openings for simultaneously extruding mass through saiddie openings, and each of said bottom walls has in its face side facingthe die when the respective pressure pot is in the extrusion position, arecess into which issue the die openings, said recess defining anextrusion pressure equalizing space.

6. The extrusion press according to claim wherein wall portions of saidbottom walls bounding said recess are in sealing engagement with the diewhen the respective pressure pot is in its extrusion position. I

7. The extrusion press according to claim 6 wherein each of said bottomwalls includes two or more nozzles, said nozzles being disposed in thebottom in concentric circles.

8. The extrusion press according to claim 7 wherein said nozzles havecross sectional areas different one from another, each of said circlesincluding nozzles of equal cross sectional area.

9. The extrusion press according to claim 8 wherein each of said bottomwalls has in its side facing the die for each of said circles an annularrecess, each of said recesses being concentrically disposed with one ofthe circles of nozzles and defining an extrusion pressure equalizingspace for the nozzles communicating with the respective recess when oneof the pressure pots is in the extrusion position.

10. The extrusion press according to claim 9 wherein said nozzles andthe respective recesses are disposed so that the cross sectional areasof the nozzles decrease in inward direction.

11. The extrusion press according to claim 10 wherein the wall portionsof the bottom walls bounding said annular recesses are in sealingengagement with the die when the respective pressure pot is in itsextrusion position.

12. The extrusion press according to claim 6 wherein the peripheral edgeof said recess defines a cutting edge for cutting massat said edge whenthe respective pressure pot is being pivoted toward the fillingposition.

13. The extrusion press according to claim 1 wherein the nozzle in eachbottom wall defines at its lower end an edge for cutting mass at saidedge when the respective pressure pot is being swung toward thefillingposition.

14. The extrusion press according to claim 1 and comprising a secondpressure means movable into and out of a pressure pot in the fillingposition for preliminarily compressing mass contained in said pot.

15. The extrusion press according to claim 1 wherein said framestructure is displaceable on the pivot means in the direction fordisplacing the bottom walls of the pressure pots into and out of sealingengagement with the pressing table.

16. The extrusion press accordingto claim 15 and comprising a closureplate on the side of the pressure table facing the pot, said closureplate being disposed to be in registry with the extrusion nozzle of apressure pot pivoted into the filling position.

17. The extrusion press according to claim 15 and comprisingspring'means biasing the frame structure and thus the two pressure potsout of said sealing position with the pressing table. 7

1. An extrusion molding press comprising in combination: a pressingtable having at least one extrusion opening therethrough; at least twosubstantially alike pressure pots open at one end and closed at theother end by a bottom wall, said bottom wall having at least oneextrusion nozzle therethrough and facing the pressing table parallelthereto; a frame structure mounting said pressure pots in spaced apartrelationship; a pivot means disposed intermediate said pressure pots andsupporting the frame structure and thus the pressure pots pivotal aboutan axis normal to the pressing table for selectively pivoting either oneof the pressure pots into a first position in which said extrusionnozzle is in registry with the table opening or into a second positionin which the extrusion nozzle is out of registry with the table opening,said first position constituting an extrusion position and the secondposition a filling position respectively for the pressure pots; and apressure means movable into and out of a pressure pot in the extrusionposition for compacting and extruding mass contained in said pot.
 2. Theextrusion press according to claim 1 wherein each of said bottom wallsis axially displaceable with the respective pressure pot.
 3. Theextrusion press according to claim 2 wherein limit means limit axialdisplacement of the bottom walLs within the pressure pots.
 4. Theextrusion press according to claim 1 wherein the nozzle in each of saidbottom walls is centrally located and has a peripheral outline largerthan the peripheral outline of an extrusion opening in the pressingplate through which the mass is to be extruded.
 5. The extrusion pressaccording to claim 1 wherein a die is fitted in the extrusion opening inthe pressing table, said die including two or more extrusion openingsfor simultaneously extruding mass through said die openings, and each ofsaid bottom walls has in its face side facing the die when therespective pressure pot is in the extrusion position, a recess intowhich issue the die openings, said recess defining an extrusion pressureequalizing space.
 6. The extrusion press according to claim 5 whereinwall portions of said bottom walls bounding said recess are in sealingengagement with the die when the respective pressure pot is in itsextrusion position.
 7. The extrusion press according to claim 6 whereineach of said bottom walls includes two or more nozzles, said nozzlesbeing disposed in the bottom in concentric circles.
 8. The extrusionpress according to claim 7 wherein said nozzles have cross sectionalareas different one from another, each of said circles including nozzlesof equal cross sectional area.
 9. The extrusion press according to claim8 wherein each of said bottom walls has in its side facing the die foreach of said circles an annular recess, each of said recesses beingconcentrically disposed with one of the circles of nozzles and definingan extrusion pressure equalizing space for the nozzles communicatingwith the respective recess when one of the pressure pots is in theextrusion position.
 10. The extrusion press according to claim 9 whereinsaid nozzles and the respective recesses are disposed so that the crosssectional areas of the nozzles decrease in inward direction.
 11. Theextrusion press according to claim 10 wherein the wall portions of thebottom walls bounding said annular recesses are in sealing engagementwith the die when the respective pressure pot is in its extrusionposition.
 12. The extrusion press according to claim 6 wherein theperipheral edge of said recess defines a cutting edge for cutting massat said edge when the respective pressure pot is being pivoted towardthe filling position.
 13. The extrusion press according to claim 1wherein the nozzle in each bottom wall defines at its lower end an edgefor cutting mass at said edge when the respective pressure pot is beingswung toward the filling position.
 14. The extrusion press according toclaim 1 and comprising a second pressure means movable into and out of apressure pot in the filling position for preliminarily compressing masscontained in said pot.
 15. The extrusion press according to claim 1wherein said frame structure is displaceable on the pivot means in thedirection for displacing the bottom walls of the pressure pots into andout of sealing engagement with the pressing table.
 16. The extrusionpress according to claim 15 and comprising a closure plate on the sideof the pressure table facing the pot, said closure plate being disposedto be in registry with the extrusion nozzle of a pressure pot pivotedinto the filling position.
 17. The extrusion press according to claim 15and comprising spring means biasing the frame structure and thus the twopressure pots out of said sealing position with the pressing table.